Method of metal plating



United States Patent 3,175,924 METHOD 9F METAL PLATING Vello Norman and Thomas P. Whaley, Baton Rouge, La.,

assignors to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Aug. 31, 1960, Ser. No. 53,026 3 Claims. (Cl. 117107.2)

This invention relates to a process for producing metallic coatings of vanadium on appropriate substrates by decomposition of organometallic compounds of such metals.

No process for plating vanadium by decomposition of organometallic compounds has heretofore been known. Present technology involves high temperature plating from the halides of vanadium by decomposition or hydrogen reduction at temperatures ranging from 800 X 1200 C. Deposition of vanadium at such high temperature requires extremely expensive processing equipment which, because of these high temperature requirements, must be constructed of a temperature resistant metal (Inconel, Hastelloy B or C, Vycor, or fused silica). High deposition temperatures give undesirable nonadherent, coarsely grained deposits. In fact at very high temperatures extremely undesirable single crystal deposits have been obtained. It is only at low temperatures that excellent, adherent, fine-grained deposits can be obtained.

Thus it can be seen that this high temperature technology involves many problems which are deterent in carrying out an economical and commercially feasible decomposition process for the plating of vanadium. A low temperature process which allows for the use of processing equipment constructed of more conventional and much more economical materials and, what is more important, produces an excellently adherent finely-grained vanadium deposit upon a wide range of substrates would be an extremely valuable contribution to this area of technology.

It is therefore an object of this invention to provide a flexible, economical process for the preparation of vanadium coatings. It is a further object of this invention to provide a process which produces extremely hard, welladhering, excellent vanadium carbide coatings as well as excellent, adherent and essentially pure metal plates thereof.

These and other objects are accomplished in accordance with this invention by providing a process for plating a wide range of substrates with vanadium, which comprises decomposition of a decomposable carbon-containing compound of vanadium in contact with the object to be plated. In this manner vanadium-containing deposits can be provided in excellent adherence upon a wide range of substrates.

A simplified flow diagram of the process is as follows:

Vaporized Group V-B metal carbon-containing compound Plating chamber Containing substrate heated up to about 400 C. Pressure from about 0.1 to about 10 mm. of mercury Plated product By decomposition as used herein is meant any method feasible for decomposing the carbon-containing compound of vanadium. Thus the term includes decomposition by ultrasonic frequency and decomposition by ultraviolet irradiation as well as by thermal decomposition. Thermal decomposition, however, is the preferred mode 3,175,924 Patented Mar. 30, 1965 of carrying out this invention because of its economical simplicity.

Therefore, within the scope of this invention is a process for plating an object with vanadium which comprises thermally decomposing a heat-decomposable carbon-com taining compound of vanadium in contact with the object to be plated, said object being heated to a temperature above the decomposition temperature of said compound.

Certain of the heat decomposable carbon-containing compounds of vanadium have low decomposition temperatures. For example, dicyclopentadienyl vanadium dibromide decomposes at about 25 C. and vanadium hexacarbonyl decomposes at about 50 C. Such low decomposition temperatures for the first time make possible a method for depositing vanadium on various low thermal stability substrates such as textiles, paper and the like.

Vanadium hexacarbonyl, because of its low decompotion temperature, is a preferred plating agent of this invention. Consequently, an embodiment of this invention is a process for plating an object with vanadium which comprises thermally decomposing vanadium hexacarbonyl in contact with the object, said object being at a temperature of about 50 C. to about C. Because of these low temperatures the object can be a material of extremely low thermal stability such as natural fibers and synthetic fibers, including paper, which are essentially stable under the conditions employed.

Although not all of the heat decomposable carbon-containing compounds of vanadium have such extremely low decomposition temperatures, it is a significant feature of this invention that most of these compounds can be decomposed at temperatures no higher than 400 C. The process of this invention is therefore a low temperature thermal decomposition process employing temperatures vastly below those of the prior art. Thus, also within the scope of this invention is a process for plating an object with vanadium which comprises thermally decomposing a heat-decomposable carbon-containing compound of vanadium in contact with the object to be plated, said object being heated to a temperature ranging from the decomposition temperature of said compound up to about 400 C.

Examples of the decomposable carbon-containing compounds of vanadium employed in this invention are dicyclopentadienyl vanadium, dicyclopentadienyl vanadium dichloride, dicyclopentadienyl vanadium dibromide, cyclopentadienyl vanadium tetracarbonyl, dibenzene vanadium, and the like.

In general any prior art technique for metal plating an object by thermal decomposition of a metal containing compound can be employed in the present plating process as long as a heat-decomposable, carbon-containing compound of vanadium, as described above, is employed as the plating agent. For example, any technique heretofore known for the thermal decomposition and subsequent plating of metals from the corresponding metal carbonyl can be employed. Illustrative are those techniques described by Lander and Germer, American Institute of Mining Metallurgical Engineers, Tech. Pub. No. 2259 (1947). Usually the technique to be employed comprises heating the object to be plated to a temperature above the decomposition temperature of the metal containing compound and thereafter contacting the metal containing compound with the heated object. The following examples are more fully illustrative of the process of this invention.

In Examples I to IV the following technique is used:

Into a conventional heating chamber, housed in a resistance furnace and provided with means for gas inlet and outlet, is placed the object to be plated. The organometallic plating agent is placed in a standard vaporization chamber provided with heating means, said vaporization chamber being connected through an outlet port to the aforesaid combustion chamber inlet means.

For the plating operation, the object to be plated is heated to a temperature above the decomposition temperature of the plating agent, the system is evacuated and the plating agent is heated to an appropriate temperature Where it possesses vapor pressure of up to about 10 millimeters. In most instances, the process is conducted at no lower than 0.01 mm. pressure. The vapors of the plating agent are pulled through the system as the vacuum pump operates, and they impinge on the heated object, decomposing and forming the metallic coating. Generally, no carrier gas is employed; however, in certain cases, a carrier gas can be employed to increase the efficiency of the above disclosed plating system. In those cases where a carrier gas is employed, a system such as described by Lander and Germer, ibid.,

page 7, is utilized.

Example I Compound C H V(CG). (cyclopentadienyl vanadium tetracarbonyl) Compound temp 80 C. Substrate Steel. Subtrate temp 250 C. Result Dark, metallic coating; contains some carbon.

Example 11 Compound C H V(-CO) Compound temp 80 C. Substrate A1 spheres. Subtrate temp 300 C. (oxygen in the plating atmosphere) Result V 0 and other oxides; catalytically active coating.

Example 111 Compound (C H V (dibenzene vanadium).

Compound temp 200 C.

Substrate Pyrex.

Subtrate temp 400 C.

Result Metallic mirror.

Example IV Compound Vanadium hexacarbonyl.

Compound temp 25 C.

Substrate, Pyrex.

Subtrate temp 100 C.

Result Metallic mirror.

The above processes employ resistance heating. The following example employs an induction heating method using higher temperatures.

The process employed in this example is essentially the same as that employed in Examples I-IV with the exception that the object to be plated is placed into a convention heating chamber provided with means for high frequency induction heating, as opposed to the former process where the heating chamber is housed in a resistance furnace.

Example V Compound (C H VCl (dicyclopentadienylvanadium dichloride) Compound temp 150 C. Substrate Al. Subtrate temp 350 C. Result Dark grey deposit.

The following example empioyes the process of Examples I-IV in the plating of vanadium from vanadium hexacarbonyl on a kraft paper substrate.

4 Example VI Compound Vanadium hexacarbonyl. Compound temp. 25 C. Substrate Kraft paper. Substrate temp. 60 C. Result Fairly shiny metallic coating.

In addition to the thermal techniques discussed hereinabove for decomposing the plating agents of this invention other methods for decomposition of these materials can be employed. The following example demon strates the decomposition of a vanadium compound by ultrasonic frequency.

The process employed in Examples I-IV is followed with the exception that an ultrasonic generator is proximately positioned to the plating apparatus. In this example the vanadium compound is heated to its decomposition threshold and thereafter the ultrasonic generator is utilized .to effect final decomposition.

Example VII Compound [(CH C H V (bis-mesitylene vanadium.

Compound temp C.

Substrate Pyrex.

Substrate temp. 300 C.

Result Dark grey deposit.

Another method for decomposing the plating agent of this invention is by decomposition with ultraviolet irradiation. The following example is demonstrative of this technique.

The method of Example I is employed, with the exception that in place of the resistance furnace there is utilized for heating a battery of ultraviolet and infrared lamps placed circumferentially around the outside of the heating chamber. The substrate to be heated is brought to a temperature just below the decomposition temperature of the plating agent with the infrared heating and thereafter decomposition is efiected with ultraviolet rays.

Example VIII Compound (C I-I V. Compound temp. 200 C. Substrate Pyrex. Substrate temp. 300 C.

Result Metallic mirror.

Other techniques besides vapor phase plating can be employed. The object to be plated can be placed in a decomposition chamber and the plating agent then packed in contact with the object to be plated and thereafter heated to a temperature above the decomposition temperature of the plating agent, whereby the volatile by-products of the decomposition reaction escape leaving an adherent metal deposit on the object. This technique can be effected in vacuo or at atmospheric pressures. An inert gas sweep can be employed to enhance removal of the by-products, although not necessary.

Some of the decomposable carbon-containg compounds of vanadium employed as plating agents in this invention have been set forth above. Further illustrative of these compounds are (dichlorophenyl methyl carbinol) vanadium carbonyl; vanadium compounds having the general empirical formula n vx Where R is a residue of an organic compound containing a five carbon ring, alicyclic in character, X is a halogen and n is 0, 1 or 2, such as dicyclopentadienyl vanadium dichloride and similar dicyclopentadienyl vanadium dihalides. Further description and methods of preparation of these vanadium compounds is to be found in U.S. Patents 2,882,288 and 2,921,948, respectively.

The substrates or objects to be plated which are utilized herein include any material which possesses sufficient structural strength under the processing conditions employed to provide a suitable support for receipt of the metal deposit which is being plated thereon. EX- amples of various substrates are Pyrex glass and spun glass; various synthetic fibers and plastics such as polytetrafiuoroethylene, polychlorotrifluoroethylene, rayon, nylon, Delrin (polyformaldehyde resin) and the like; steel, such as nickel plated steel, mild steel, nickel plated mild steel; metallic turnings such as copper, zinc and the like; cellulose materials such as cotton, paper and the 1ikein short, any material essentia ly stable under the plating conditions employed. Thus, further demonstrative of the substrates of this invention are carbonaceous materials, such as graphite; other refractory substrates, such as Carborundum, ceramics, cermets and the like; other metallic substrates such as aluminum, titanium, vanadium, yttrium, copper zinc, cadmium and the like; nuclear reactor fuel elements such as uranium 235, uranium 233, thorium and other fissionable materials.

When conducting the process of this invention, it is important to maintain enough vapor pressure below the decomposition temperature of the organometallic plating agent to enable the process to be conducted at an appreciable rate of plating. Too high vapor pressure results in somewhat inferior substrate adherence. Thus, it is preferred to employ up to about 10 mm. pressure during the plating operationpreferably 0.01 to 10 mm. pressure.

In conducting the process of this invention temperatures are very important in obtaining the desired plated product. Thus although temperatures above the decomposition temperature of the heat decomposable carboncontaining compound of vanadium utilized in this invention can, in general, be employed in the plating process, best results are obtained within certain preferred temperature ranges. For example, excellent, essentially pure bright vanadium plates are produced at temperatures ranging from the decomposition temperature of the plating agent up to about 50 C. above the decomposition temperature. Metallic mirrors are produced up to about 100 C. above the decomposition temperature. Higher temperatures produce carbon-containing deposits. Generally temperatures of 550600 C. produce very hard carbide coatings. It will be understood that these temperature ranges will vary somewhat depending upon the particular compound use in the plating operation.

The plating compounds of the present invention vary insofar as their thermal stability is concerned but generally all of them can be decomposed at a temperature above 400 C. It has not been found necessary to employ temperatures any higher than 600 0, although higher temperatures could undoubtedly be employed with substrates having suflicient structural strength at these higher temperatures.

The metal plates produced by the process of this invention find a multitude of uses in the aircraft, missile and chemical processing industries. Thus aircraft and missile components which require ultra high quality performance characteristics such as resistance to high temperatures, Wear resistance and resistance to chemical attack can satisfactorily meet these requirements when coated with vanadium produced according to the process of the instant invention.

The metal carbide coatings which are so conveniently prepared by the process of this invention find particular applicability in utilities Where their excellent high temperature and wear resistance properties come into play. Such applications are as coatings for dies, such as when an automotive die is coated with vanadium to produce a hard vanadium metallic coating by the process of the instant invention.

Having thus described and demonstrated the instant invention, it is not intended that the scope thereof be limited in any way except as set forth in the following claims.

We claim:

1. A process for depositing a coating on a substrate which process comprises decomposing cyclopentadienyl vanadium tetracarbonyl in contact with the substrate at a pressure ranging from about 0.1 millimeter to about 10 millimeters of mercury and at a temperature of up to about 400 C.

2. A process for depositing a vanadium coating on a substrate which process comprises decomposing dicyclopentadienyl vanadium dibromide in contact with the substrate at a pressure ranging from about 0.1 millimeter to about 10 millimeters of mercury and at a temperature of up to about 400 C.

3. A proces for depositing a vanadium coating on a solid substrate, which process comprises contacting a cyclopentadienyl vanadium tet'racarbonyl vapor with a solid substrate that is heated .to a temperature of up to about 600 C. and sufficient to decompose said cyclopentadienyl vanadium tetracarbonyl and deposit the desired coating.

References Cited by the Examiner UNITED STATES PATENTS 2,818,416 12/57 Brown et a1.

2,868,697 1/59 Bingeman et al.

2,885,310 5/59 Olson et a1 117-107 2,930,767 3/60 Novak 117107 2,953,586 9/60 Hafner et a1.

2,955,958 10/60 Brown 117--113 OTHER REFERENCES Lander et al.: Plating Molybdenum, Tungsten and Chromium by Thermal Decomposition of Their Car- 'bonyls, A.l.M.M.E. Technical publication No. 2259, September 1947 (pages 6 and 7 relied on).

RICHARD D. NEVIUS, Primary Examiner.

JOSEPH B. SPENCER, Examiner.

. STA'IES PATENT OFFICE CERTIFICATE OF CORRECTION ?atent No. 3 ,175,924 March 30, I965 Vello Norman et al0 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 1 line 56, beginning with "vaporized" strike out all to and including "Plated product" in line .66, same column 1, and insert instead the following Vaporized Croap V-B metal carbon-containing compound Plating chamber Containing substrate heated up to about 400 C. Pressure from about 0.1 to

about 10 mm. of mercury Plated product Signed and sealed this 14th day of June 1966,

(SEAL) Ittest:

ERNEST W. SWIDER EDWARD J. BRENNER \ttesting Officer Commissioner of Patentsv UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,175 ,924 March 30, 1965 Vello Norman et a1.

' It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 56, beginning with "Vaporized" strike out all to and including "Plated product" in line 66, same column 1, and insert instead the following Vaporized Group V-B metal carbon-containing compound Plated product Signed and sealed this 14th day of June 1966.

(SEAL) Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR DEPOSITING A COATING ON A SUBSTRATE WHICH PROCESS COMPRISES DECOMPOSING CYCLOPENTADIENYL VANADIUM TETRACARBONYL IN CONTACT WITH THE SUBSTRATE AT A PRESSURE RANGING FROM ABOUT 0.1 MILLIMETER TO ABOUT 10 MILLIMETERS OF MERCURY AND AT A TEMPERATURE OF UP TO ABOUT 400*C.
 2. A PROCESS FOR DEPOSITING A VANADIUM COATING ON A SUBSTRATE WHICH PROCESS COMPRISES DECOMPOSING DICYCLOPENTADIENYL VANADIUM DIBROMIDE IN CONTACT WITH THE SUBSTRATE AT A PRESSURE RANGING FROM ABOUT 0.1 MILLIMETER TO ABOUT 10 MILLIMETERS OF MERCURY AND AT A TEMPERATURE OF UP TO ABOUT 400*C. 